In Great Britain, the composition of mortar does not seem to have occupied much of the attention of the learned, prior to the beginning of the 18th century, or the time of Sir Christopher Wren. And, indeed, the subject was not pursued with much intelligence and effect, till after the great discoveries of Dr Black, about the year 1754, which unfolded the principles of latent caloric, and the expulsion of fixed air, by which limestone loses about one-half of its weight in the process of calcination. These discoveries were succeeded by the excellent treatise of Dr Higgins on Water Cements, published in 1780; and in 1793, Mr Smeaton’s Narrative of the Edystone Light-house appeared, containing, not only an account of the preparation of the mortar for that celebrated building, but also of his experience for thirty-six years, as an engineer of the most extensive practice of his day. The composition of mortar has also occupied the attention of several French authors, as Belidor, Loriot, Viccat and others, but without perhaps adding much to our stock of practical knowledge. [Sidenote: Experience of the writer.] Were the writer permitted to state the result of his professional observations for the last twenty years, he might notice, that no error is more commonly met with in water buildings, than that of employing house or common mortar in the erection of sea-walls. It may also be stated, generally, in compounding mortar, that the cheapest article is too apt to be made use of in the greatest proportion. We accordingly find, that lime is not unfrequently made too _rich_, as it is technically termed when a small proportion of sand is applied to the mixture; an error, which is attended even with worse consequences than when the lime is made _poor_, or when too great a proportion of sand is used. But, perhaps, the worst of all mortar is that wherein very fine _pit-sand_, containing a portion of earthy matters, is used, and when the whole is mixed up with impure water. So little attention is often paid to the quality of mortar, in common buildings, that one would imagine it were applied, as if intended more to prevent the sifting winds from penetrating the walls, than as the medium by which they were ultimately to be bound or formed into a compact fabric.